Extensometers for materials testing
High Temperature Axial/Torsional Extensometers (1200°C or 1600°C) – Model 7650
Simultaneously measures axial and torsional strains at high temperatures on specimens tested in axial/torsional machines. For use with materials testing furnaces or induction heating up to 1600 °C (2900 °F). May be used for bi-axial strain controlled fatigue. Slide mounting system enables mounting to hot specimens in seconds.
Epsilon extensometers are COMPATIBLE WITH VIRTUALLY EVERY BRAND OF TEST EQUIPMENT and can be supplied with the correct connector to plug in directly.
Operation of these, and all of Epsilon’s extensometers, are
VERIFIED TO APPLICABLE STANDARDS SUCH AS ASTM E83 OR ISO 9513
using in-house calibration systems that are calibrated with Epsilon’s laser interferometer system.
WITH EPSILON’S 20+ YEAR HISTORY OF SERVICE
to the materials testing community, you know we will be there to stand behind our products when your critical application requires it.
Model 7650 extensometers are primarily used on round specimens tested in bi-axial test machines capable of simultaneous axial and torsional loading. All models are capable of bi-directional displacement in both axes and may be used for strain-controlled fatigue testing under fully reversed load and strain conditions at frequencies up to 10 Hz.
All 7650 models mount rigidly on the load frame and incorporate slide mounting to bring the extensometer into contact with the specimen. The gauge length is set automatically before mounting on the test specimen, which allows for hot mounting after thermal equilibrium has been reached.
These units are specifically designed to minimize crosstalk between axes and to provide high accuracy, high resolution measurements. They incorporate capacitive sensors for low operating force and include electronics with programmable filtering and multi-point linearization for improved performance and accuracy. The overall design minimizes, and in many cases virtually eliminates, any influence from common lab environment vibrations.
These water-cooled extensometers are equipped with high purity alumina rods with conical rod tips for specimen contact when testing to 1200 °C (2200 °F). Silicon carbide rods are used for the 1600 °C (2900 °F) high temperature option.
The Model 7650 is often customized for specific test needs. Contact Epsilon for a configuration that matches your requirement.
- Hot mountable and retractable.
- Self-setting gauge length with fine adjustment feature.
- All models can measure in both tension and compression and may be used for cyclic testing at test frequencies up to 10 Hz.
- Standard units meet ASTM class B-1 requirements for accuracy (axial). A test certificate is included. ISO 9513 class 0,5 test certificates are available upon request.
- Ships fully calibrated with calibration that is traceable to NPL; voltage output may be user-specified (typically 0-10V).
- Excellent ambient vibration rejection; primary vibration mode >100 Hz typical
- Digital controller and power supply included. Provides high level DC voltage output with low noise. Easily interfaced to test controllers, data acquisition boards and chart recorders.
- Includes high speed analog and digital outputs.
- Web-based user interface for setup and data acquisition.
- Selectable analog and digital filter options from 2 Hz to 3 kHz.
- Built-in calibration reference and auto-zero features.
- Multiple extensometer calibration files may be loaded for use with one controller.
Analog Output: User specified, ±10VDC typical, ±10.8VDC rail
Digital Output: 24 bit high speed Ethernet output with built-in web interface
Cyclic Testing: up to 10 Hz, depending on test system and test amplitude
Linearity: 11 point digital linearization, ≤0.1% FS typical linearity (axial and torsional)
Hysteresis: ≤0.1% FS typical
Crosstalk: ≤0.2% FS typical at ±1° shear with 25 mm diameter specimen and 12.5 mm gauge length
Resolution: <75 PPM (0.0075%FS) RMS @ 4 kHz, <6 PPM (0.0006%FS) @ 100 Hz at gauge length
Filter: Selectable 100 Hz analog and 2 Hz – 3 kHz digital filters
Sensor Cables: 2m (6.5 ft) room temperature cables
Output Cables: Flexible 2.4 m (8 ft) analog output cables
Specimen Size Range: Fits most round specimen diameters
Test Frame Layout: Accommodates test frames with torsional actuator located above or below specimen
Operating Force: <30 grams typical
Contact Force: <560 grams typical
Environment: Recommended for testing in dry air, inert / non-corrosive gases, or vacuum
Power: Includes power supply for your country
- High temperature option (-HT suffix) for use to 1600°C
- Load frame mounting brackets
- Bulkhead adapters for use in vacuum chambers
- Model 2050 constant temperature water re-circulating bath
- Connectors to interface to nearly any brand test equipment
- See Epsilon’s Axial/Torsional Extensometer Calibrator
Epsilon’s axial/torsional extensometer was designed to directly measure the shear strain, γ, shown in the figure. This design allows the correct determination of the shear strain without having to know the radius of the specimen being tested, R1. The shear strain is related to the angle of twist (a commonly referenced parameter in torsion testing), φ, by the following relationship:
For extensometers that measure φ directly instead of γ, corrections need to be made for every different specimen diameter tested and for axial strain to correctly determine the shear strain. The following two examples show the variation of the angle of twist versus a change in specimen diameter relative to the constant resulting shear strain:
Model Number: 7650 – 0125M – 025M – 020 – ST
7650 – 0125M – 025M – 020 – ST
12.5 mm gauge length, +2.5 mm / -0.5 mm axial, ±2° torsional, room temperature to 1200 °C
Model Number: 7650 – 025M – 025M – 010 – ST
7650 – 025M – 025M – 010 – ST
25 mm gauge length, +2.5mm / -0.5mm axial, ±1.0° torsional, room temperature to 1200 °C
Other configurations are available, such as ±1.5 mm axial measuring range – please contact Epsilon to discuss your requirements. Up to ±4° torsional measuring range is available (gauge length dependent), and up to 3 mm of axial measuring range is available.
Room temperature to 1200 °C (2200 °F) -ST
Room temperature to 1600 °C (2900 °F) -HT
Ceramic rod lengths are made to fit furnaces as required. Specify specimen diameter, load frame configuration, furnace dimensions, and electrical outlet type at time of ordering.
Requires external mounting brackets and 110 – 240VAC / 4W electrical power. Water cooling is recommended; required for 1000 °C and above.